As mobility management protocol for a mobile node performing internet protocol communication (IP communication) in conventional mobile communication systems, Mobile IPv4 (MIPv4) or Mobile IPv6 (MIPv6) has been used. Details of these technologies are disclosed in Non-patent Document 1 and Non-patent Document 2, below. In addition, conventionally, Dual Stack Mobile IP (DSMIP) has been used that expands MIPv6 operating only in access networks supporting IPv6 to also operate in access networks supporting only IPv4. Details of this technology are disclosed in Non-patent Document 3.
A mobile node registers an IPv6 home address (HoAv6) and an IPv6 care-of address (CoAv6) in a home agent (location management server) using MIPv6 protocol based on Non-patent Document 2, and the home agent manages correlation (binding) of the addresses. However, all messages are based on IPv6 protocol and can only be used in accesses networks supporting IPv6. DSMIP is an expansion of MIPv6 and, when the mobile node attaches to an access network supporting only IPv4, enables communication using the HoAv6 even from the access network supporting only IPv4 by binding an IPv4 care-of address (CoAv4) acquired from the access network with the HoAv6.
Furthermore, under a premise that the home agent has an IPv4 address, the DSMIP enables exchange of binding control messages (such as binding update (BU) and binding acknowledge (BA) messages) based on MIPv6 by encapsulating the CoAv4 and the IPv4 address of the home agent by an IPv4 header contained in an address field, and enables communication with a correspondent node (CN) having only an IPv4 address by allocating an IPv4 home address (HoAv4) to the mobile node.
A method of enabling MIPv6-based binding management of a mobile node attached to an access network supporting only IPv4 is also disclosed in Patent Document 1, below. A handover method using similar technology is being examined for use in mobile communication systems for mobile phones, as well. In Non-patent Document 4, below, a method of performing a handover from a 3GPP access network (such as LTE) to a non-3GPP access network (such as a wireless LAN network system, a WiMAX network system, or a 3GPP2 network system) using DSMIP is disclosed.